When you run the script/generate command, you specify
the name of the model, the names of the columns, and the types for the data
contained in the columns.

A scaffold is the set of code that Rails generates to handle database
operations for a model object, which is Book in this case.
The scaffold consists of a controller and some views that allow users to perform
the basic operations on a database, such as viewing the data, adding new records,
and editing records. Rails also creates the model object when generating the
scaffold.

Create the database tables:

jruby -S rake
db:migrate

When Rails is finished creating the tables, you should see output similar
to the following:

CreateBooks: migrated (0.1322ms) =========

If you need to reset the database later, you can run the following command: